Electrical circuit wiring arrangement and its soldering method

ABSTRACT

A method of manufacturing an electrical circuit wiring assembly comprises the steps of preparing a first sub-assembly having a metal board chassis and a first circuit element provided with hard stiff leads, preparing a second sub-assembly having a second circuit element provided with soft thin leads and an eyelet terminal for connecting the soft thin lead to the hard lead by means of a soldered junction, and assembling the first and second sub-assemblies by a soldering operation to form a main wiring assembly. In the second sub-assembly the second circuit element and the eyelet terminal are carried temporarily on an unsolderable mounting tool. The first and second sub-assemblies are temporarily coupled to each other during the forming of the main assembly by means of a coupling tool or jig for applying molten solder to an exposed connecting portion of the eyelet terminal and to portions of the hard and soft leads extending from the eyelet terminal. After soldering, the unsolderable mounting tool and the coupling tool are removed from the soldered main wiring assembly so that a three-dimensional wiring assembly is obtained.

BACKGROUND OF THE INVENTION

This invention relates to a method for manufacturing an electricalcircuit wiring arrangement for use in high frequency tuning circuits fortelevision receivers, and more particularly, to a soldering method ofthe circuit elements in the wiring assembly constructed for facilitatingthe mounting of the circuit elements.

Generally, electrical circuit wiring arrangements or systems fall intotwo groups, namely, the two-dimensional printed wiring system or thethree-dimensional wiring system. In printed circuits a sheet ofinsulating material is used as a printed circuit board which isadvantageous for an automatic assembly and soldering, but the screeningeffect of a metal chassis is lacking. The insulating material of theprinted circuit board increases the capacitances between theconnections. Moisture can cause some conduction along the surface of theprinted circuit board. On the other hand, a manual wiring system orso-called "jungle" wiring system is advantageous for achieving desirablehigh frequency characteristics due to diminishing stray capacitances,and for desirable economical and space-factor aspects without using anyprinted circuit board.

The following are the good aspects of the two-dimensional configurationand of the three-dimensional configuration of wiring systemsrespectively. A two-dimensional configuration printed wiring system hasthe following advantages. (1) The final assemblies are very constant intheir characteristics from one set to another, (2) compensations can beintroduced in the wiring itself, (3) the circuit arrangement is verydistinct and neat with all points readily accessible, and (4) theassembling and soldering are suitable for an automatic production or anassembly line. In the so-called jungle wiring system having athree-dimensional configuration the advantages are as follows, (1) allcritical connections can be short, because they can cross each other,(2) capacitances are low, mutually and with respect to the chassis, (3)the wiring has a small surface area, and (4) a printed circuit board forsupporting the circuit elements is eliminated.

It is therefore desirable to provide an improved system having theseadvantages of the conventional systems in combination. In other words,it is sought to apply an automatic soldering method for producing ajungle wiring system in the same manner as that for the printed wiringsystem. Conventional wiring systems still leave room for improvement,especially as far as minimizing the assembly size and dimension isconcerned. This applies to simplifying the assembly, as well as tolowering the manufacturing costs and to improving the electricalperformance of these circuits.

OBJECTS OF THE INVENTION

In view of the foregoing, it is the aim of the invention to achieve thefollowing objects singly or in combination:

to provide a method for manufacturing a new and improved electricalcircuit wiring arrangement for high frequency applications, wherein aneasily assembled construction simplifies the circuit arrangement of thejungle wiring system and wherein the number of printed circuit boards isreduced, whereby the circuit arrangement may be manufactured withsub-assembly techniques in an economic manner;

to provide a new and improved electrical circuit wiring assembly for ahigh frequency tuner construction mounted on the chassis base in such asub-assembly manner that mass production methods may be employed for itsmanufacture;

to provide a low cost and small size electrical circuit wiring assemblyfor soldering circuit elements without using any printed circuit board;

to provide a new and improved soldering method for electrical circuitwiring arrangements using circuit element supporting means instead of aprinted circuit board; and

to provide an improved and simplified manufacturing method for a highfrequency circuit assembly using eyelet terminals to electrically andmechanically connect different type circuit elements to each other,whereby jig or mounting tool means for supporting the eyelet terminalsare employed in an automatically simplified step of dip-soldering forconnecting first and second circuit elements to each other as well asfor connecting soft and thin leads of second circuit elements to eachother.

SUMMARY OF THE INVENTION

This invention provides a method for manufacturing an electrical circuitwiring arrangement having different types of circuit elements, one ofwhich includes a hard and stiff lead portion and the other of whichincludes a soft and thin lead portion. The stiff leads of the first typeof circuit elements are mounted on a plate metal chassis base by a stepof relatively high temperature soldering whereby the stiff lead portionsextend from said chassis base. The thin leads of the second type ofcircuit elements are connected to the extending stiff lead portions andto each other by means of eyelet terminals located near one side of thechassis base. Each eyelet terminal is soldered to connect the leads ofthe first and/or second circuit elements by a soldering operationsimilar to that used in a two-dimensional configuration as well as thatused in printed circuit wiring. A jig or mounting tool in the form of anunsolderable supporting plate such as synthetic resin or stainless steelis employed to temporarily hold the eyelet terminals. The mounting toolis provided with through-holes for receiving each eyelet terminal duringproduction steps including at least the inserting of the leads,soldering, cutting undesired lead portions, and re-soldering forcorrecting any bad connection. The soft leads of the second circuitelements are connected to the eyelet terminals and to the hard leads ofthe first circuit elements mounted on the chassis base.

In one aspect of this invention, an electrical circuit wiringarrangement useful for high frequency circuits such as a televisiontuner, comprises a plurality of first circuit elements having stiffleads, a metal board of a shielding chassis base, a plurality of secondcircuit elements having thin leads, and terminal means for connecting astiff lead and a thin lead with solder to form a given circuit, whereinthe first circuit elements are fixed to the metal board of the chassisbase by a first type of soldering material, and the second circuitelements are connected electrically and mechanically to each otherand/or to predetermined first circuit elements by terminal means in theform of a soldered junction. In this manufacturing process the secondcircuit elements are supported by unsolderable supporting means forlocating the second circuit elements near the chassis base to solder theconnecting points of the lead portions. It is advantageous to use eyeletterminals for the soldered junctions of the leads or terminal means andto use an unsolderable mounting jig or tool such as a stainless steelplate as a supporting means which is removable from the completedcircuit wiring so as to repeatedly employ the mounting tool in themanufacturing process.

This circuit wiring assembly is very advantageous because it improvesthe high frequency characteristics without using any printed circuitboards and it reduces the production costs. Particularly, since theeyelet terminals guide both types of leads, the connections between thefirst and second circuit elements are achieved effectively by solderingportions of the stiff leads of the first circuit elements and/or thethin leads of the second circuit elements together with the eyeletterminals which are mounted on the unsolderable supporting means atgiven positions. In one practical use, the circuit wiring assembly ofthis invention is useful in stator side tuner circuits of VHF tuners,for example. In such a case, a top wall of the chassis base is used asthe metal board on which the first circuit elements such as earthterminals, phono-jacks, through-type capacitors and the like are fixedby the specific shape of the solder material to form a firstsub-assembly for the first circuit elements. On the other hand, thesecond circuit elements include in this example tuning parts such ascoils, capacitors, resistors, diodes, transistors and the like which areconnected by low temperature molten solder material at the lead portionsof the circuit elements extending from the eyelet terminals. The secondcircuit elements are located near one side of the metal board chassisbase and between the eyelet terminals. The first and second circuitelements are connected to each other in the eyelet terminals by themolten solder which easily bonds to the leads and to the eyelets byfilling any voids in the eyelet due to capillary action.

Another aspect of this invention provides an improved manufacturingprocess for the circuit wiring assembly, which comprises first solderinga plurality of first circuit elements to a metal board chassis base as afirst sub-assembly, preparing a jig or mounting tool in the form of asupporting plate made of a material that cannot be soldered, with aplurality of through-holes for receiving eyelet terminals in a removablemanner, inserting the thin leads of a plurality of second circuitelements into the eyelet terminals so as to form a second sub-assembly,assembling the first and second sub-assemblies to form a main assemblywith a given space between the chassis base and the supporting plate byinserting stiff leads of the first circuit elements into a tube portionof the eyelet terminals by using an assembly tool, second soldering alllead portions in the eyelet terminals to electrically and mechanicallyconnect the leads and eyelet terminals for forming soldered junctions ofthe circuit wiring, and removing the mounting tool from the solderedjunctions of the second sub-assembly. If necessary, any excessive leadlengths may be cut off.

Any defective soldered junctions may be corrected in a third resolderingstep to repair voids and cracks in the eylet terminal.

The first soldering step is performed by using ring-shaped solder havinga relatively high melting temperature whereby the first circuit elementsare assembled on the metal board of the chassis base as the firstsub-assembly. That is, the first circuit elements of the firstsub-assembly are solidly fixed automatically by the solder due toheating in a conveyor type furnace. In contrast to the first solderingstep, the second and third soldering steps are performed by using solderhaving a relatively low melting temperature. However, each solderingstep may be performed by the same dip-soldering method as is used in aprinted circuit board wiring system, for example, by the use of a jetstream type automatic soldering equipment for printed circuit boardassemblies.

The manufacturing of the circuit wiring assemblies of this invention iscapable of being automatically performed in a manner used for makingordinary printed circuit board assemblies. One important advantageouseffect of the present method using eyelet terminals is obtained by thecapillary effect which causes the molten solder to fill these eyeletterminals. Another advantage resides in the use of jig or mounting toolsfor the soldering steps without using any printed circuit board, and thedisposition of each circuit element is kept strictly in the correctposition because the second and/or third soldering steps are done in theassembled state of the mounting and assembly tools. The third solderingstep is applied only for correcting any defective soldered contact afterthe cutting step for removing any unnecessary lead portions.

The present circuit wiring assembly has especially advantageouselectrical characteristics for application to high frequency circuitssuch as VHF tuner circuits for a turret type tuner comprising arotatable tuning selecting mechanism and a stationary main circuit. Thepresent electrical circuit wiring assembly is also advantageous fromeconomical view points. That is, when the main circuit of the statorside is assembled on the top wall of the shielding chassis base and thechannel selection is done by switching a plurality of tuned coilsegments disposed in the rotatable turret body, the stator side circuitof this invention allows for and contributes to an automatic andsimplified assembly. Additionally, it stabilizes and improves theperformance of the high frequency characteristics of such tuners.

BRIEF FIGURE DESCRIPTION

In order that the invention may be clearly understood, it will now bedescribed, by way of example, with reference to the accompanyingdrawings, wherein:

FIG. 1 is a side plan view partially in section of a conventionalcircuit assembly,

FIG. 2 is a side view partially in section of an electrical circuitwiring assembly of this invention;

FIG. 3 is a side view of a portion of FIG. 2, showing a stage afterforming a first sub-assembly of first circuit elements on a metal boardor chassis base;

FIG. 4 is a side view similar to that of FIG. 3, but showing a stageafter forming a second sub-assembly of second circuit elements on anunsolderable supporting plate of a mounting tool or jig;

FIG. 5 is a partially perspective view of the sub-assembly of FIG. 4;

FIG. 6 is a side view similar to that of FIG. 3, but showing a finalassembling stage illustrating the relationship of the first and secondcircuit elements;

FIG. 7 is an enlarged view of a portion of FIG. 6;

FIG. 8 is a circuit diagram of another embodiment of a circuit wiringassembly used in a turret type VHF tuner of this invention;

FIG. 9 is a side view of the VHF tuner assembly illustrated in FIG. 8;

FIGS. 10 to 12 are respectively sectional views of an assembly of thecircuit of FIG. 8, and showing each of the steps in the assemblingprocess;

FIG. 13 is an enlarged view of a portion of the assembly of FIG. 12illustrating the condition after the second soldering step;

FIG. 14 is an enlarged view of a portion of the assembly of FIG. 12, butnow showing the completed state;

FIG. 15 is a top plan view of a tuner including the assembly of FIG. 8;

FIG. 16 is a side view of the tuner of FIG. 15; and

FIG. 17 is an exploded view of a stator side of the tuner of FIG. 15.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BESTMODE OF THE INVENTION

The electrical circuit wiring assembly of this invention is explained byreferring to FIGS. 2 to 7 in comparison to a conventional circuit wiringassembly shown in FIG. 1. In FIG. 1, the conventional three-dimensionaltype jungle circuit assembly comprises a metal board 1, a plurality offirst circuit elements 2 with stiff leads 3, and a plurality of secondcircuit elements 4 with thin leads 5, wherein each of the first circuitelements 2 inserted into each through-hole 6 of the metal board 1 issoldered thereto by soldering material 7, and each of the thin leads 5of the second circuit elements 4 is connected with a respective stifflead 3 of the first circuit element 2 by a soldered junction 8. However,such conventional soldered junctions have been made by a manualsoldering method employing a soldering iron 9, which makes theassembling work very difficult and complicated.

According to this invention the manufacturing of an electrical circuitwiring assembly has been adapted to an automatic manufacturingoperation. According to FIGS. 2 to 7, the circuit wiring process of thisinvention includes three steps of first soldering for forming a firstsub-assembly 10 including a chassis base 11 of a metal board and aplurality of first circuit elements 12 with stiff leads 13; preparing asecond sub-assembly 20 shown in FIG. 4 including an unsolderablesupporting board 21 as a mounting tool or jig, eyelet terminals 22disposed at the receiving holes 23 and a plurality of second circuitelements 24 with thin leads 25. A second soldering step results in acombination or main assembly 30 including the first and secondsub-assemblies 10 and 20. In the first sub-assembly 10 of FIG. 3, thefirst circuit elements 12 are fixed on the chassis base 11 respectivelyby soldering material 14 connecting the flange portion 15 of eachcircuit element 12 to the peripheral portion near the through-hole 16 inthe chassis base 11. In FIGS. 4 and 5, the second circuit elements 24 ofthe second sub-assembly 20 are positioned on the supporting board 21 andeach thin lead 25 of the elements 24 is inserted into an eyelet terminal22 located in a respective receiving hole 23. In FIG. 6, the first andsecond sub-assemblies are combined to provide a given spacing betweenthe chassis base 11 and the supporting board 21, and the secondsoldering step is applied to form soldered junctions 19 in each eyeletterminal 22. As shown in FIG. 7, the soldering material of the junction19 is introduced into each eyelet terminal due to the capillary actionof the eyelet on the molten solder. Any unnecessary soldering portionmay be cut off as shown by the dash-dotted line, to make the finishedproduct compact and suitable for high frequency circuit applications.

FIG. 8 is a circuit diagram of another embodiment used in a turret typeVHF tuner which comprises rotor means of a UIF tuning unit 41, aplurality of VHF tuning units 42, and stator means of a wiring assembly40 of this invention. The stator and rotor are electrically connected bya plurality of contact terminals 43. The feature of the circuit wiringassembly 40 is to use eyelet terminals at soldered junctions 44. Forinstance, the eyelet terminals are used at twenty junctions 44. Asdescribed with reference to FIGS. 2 to 7, some soldered junctions 44 areheld by stiff leads of the first circuit elements 12 such asthrough-type capacitors, earth terminals, and phono-jack terminals whichare fixed to the chassis base or metal board. Input, output andoperating source terminals for the tuner circuit wiring assembly areprovided by a phono-jack type UIF input terminal UIF-IN, a VHF inputterminal V-IN, and an IF output terminal IF-OUT. Also, the stiff leadsof the through-type capacitors provide an automatic gain controlterminal AGC, a power source terminal +B, an AFT signal terminal AFT anda UHF power source terminal UB.

FIGS. 9 to 14 are similar to FIGS. 2 to 7 and provide explanatorydiagrams regarding each manufacturing step for making a circuit wiringassembly 40 of this invention. In FIG. 9, the completed circuit wiringassembly 40 includes a plurality of first circuit elements such asphono-jacks 51, through-type capacitors 52 and an earth terminal 53fixed with solder 54 on the metal board chassis base 50. Stiff leads 55of the first circuit elements are connected in a three-dimensional orjungle type wiring system at one side of the chassis base 50 with thinleads 60 of a plurality of second circuit elements such as resistors 57,capacitors 58, and transistors 59 at each eyelet terminal 56. Thiscircuit wiring assembly can maintain a favorable high frequencycharacteristic performance due to the correct disposition of the circuitelements at fixed positions in the given space without using any printedcircuit boards. Accordingly, undesirable coupling effects and lossescaused by stray capacitances for high frequency signals are eliminated.Economical merits are also achieved due to reducing the cost for printedcircuit boards.

FIGS. 10 to 14 show sectional views for each manufacturing step of thecircuit wiring assembly 40 of FIG. 8 of this invention. In FIG. 10, afirst sub-assembly 45 includes the first circuit elements provided withstiff leads 55, such as phono-jacks 51, through-type capacitors 52 andan earth terminal 53, and the metal board chassis base 50 is providedwith through-holes to let pass through the stiff leads 55 and to fixeach first circuit element by the respective ring shaped first soldermaterial 54 around each through-hole in the base 50. Under suchcondition, the first circuit elements and the chassis base are solidlyinterconnected by passing through a soldering furnace to melt the firstsolder material 54. The step of first soldering is made in the furnacehaving a comparatively high temperature such as about 350° C., wherebythe first soldering step is done at a higher temperature than that of asecond soldering step of 260° C. for the final assembly as mentionedhereinafter.

In FIG. 11, a second sub-assembly 46 for second circuit elements such asresistors 57, capacitors 58 and transistors 59 provided with thin leads60 comprises a mounting tool or jig 61 of an unsolderable supportingplate with through-holes and a plurality of eyelet terminals 56 receivedin these through-holes. The mounting tool 61 is made of stainless steelor the like which cannot be soldered. The automatic insertion of theeyelet terminals 56 into each through-hole and the insertion of thesecond circuit element into each eyelet terminal 56 are done easilythereby facilitating the assembling work efficiency. In FIG. 12, acombination or main assembly 47 of these two sub-assemblies 45 and 46shown in FIGS. 10 and 11, is prepared by utilizing a lower assembly tool62 and an upper assembly tool 63. Thus, the stiff leads 55 extendingfrom the chassis base 50 are inserted into the eyelet terminals 56received in the mounting tool 61, so as to provide a space between thechassis base 50 and the mounting tool 61 and to hold them in a fixedstate by coupling both assembly tools 62 and 63 to each other. Forinstance the first sub-assembly 45 on the chassis base 50 on which thefirst circuit elements 51 to 53 are fixed by soldering, is placed abovethe second sub-assembly 46 on the mounting tool 61 on which the eyeletterminals 56 and the second circuit elements 57 to 59 are assembled,whereby the lower assembly tool 62 holds both assemblies while the upperassembly tool 63 holds both assemblies in place. The combination 47 ofthe sub-assemblies is held by these jig means 62 and 63 in properpositions until the completion of the final soldering step. Thecombination is treated with a flux application and dipped into moltensolder as is the case in soldering of ordinary printed circuit boards.In a usual jet stream or flow soldering method, the inside portion ofeach eyelet terminal is wholly wetted with molten solder, then each ofsoldered junctions 64 is formed due to the action of the surface tensionof the molten solder, whereby the solder crawls up within each eyeletterminal 56. This is enhanced by capillary action.

The soldered junctions 64 in an incomplete assembly 48 may have anon-uniform shape after the second soldering treatment, as an icicle asshown in FIG. 13, and such unnecessary lead portions are removed by acutting step. After cutting unnecessary lead portions 64 properly,sometimes caves, crevices and void portions are found inside of theeyelet terminals 56, but such portions are filled with solder by acorrecting third soldering step. FIG. 14 shows the complete solderedjunctions 65 after the third soldering. After the third soldering hasbeen completed, the lower and upper assembling tools 62 and 63 and themounting tool 61 are removed from the completed wiring assembly 40.

The third soldering step is performed in the same manner as the secondsoldering. If the third soldering is done when the incomplete assembly48 is still at a relatively high temperature, it is difficult to applysoldering flux. In such a case, the flux is applied by means of arotating mat impregnated with flux to those portions requiring the thirdsoldering. The mat avoids that flux bubbles are broken off by the jigassembly at a high temperature. The important features of the abovementioned electric circuit wiring assembly of this invention make itpossible to use printed circuit soldering techniques without using anyprinted circuit boards, and to obtain a desirable three-dimensional orjungle type wiring system suitable for high frequency circuits.Accordingly, the cost of required parts is reduced by the omission ofthe printed circuit boards, and the assembling cost is also reduced bythe application of automatic soldering to the three-dimensionalconfiguration system. The soldering steps are performed by an apparatusof the same type as is used for soldering printed circuit board wiringsystems whereby manual soldering is avoided. Consequently, aneconomically and characteristically improved electric circuit wiringassembly is produced by this invention.

FIGS. 15 to 17 show a turret type VHF tuner as disclosed in thecopending application Ser. No. 133,604 filed Mar. 24, 1980, wherein thecircuit wiring assembly 40 of FIG. 8 is mounted on a chassis frame 70. Achannel selector shaft 71 is journaled with detent means on the chassisframe 70, and a fine tuning mechanism 72 is mounted around the selectorshaft 71. Open portions of the chassis frame 70 are covered by a shieldcover 73. FIG. 17 shows a partial exploded view of this tuner, whereinthe circuit wiring assembly 40 is coupled to the top of the chassisframe 70. A stator bar 74 with stator contacts 43 is operatively held inthe frame 70.

Although the invention has been described with reference to specificexample embodiments it will be appreciated that it is intended to coverall modifications and equivalents within the scope of the appendedclaims.

What is claimed is:
 1. A method of manufacturing an electrical circuitwiring on metal board means for supporting a plurality of first circuitelements with hard leads, a plurality of second circuit elements withsoft leads, and a plurality of eyelet terminals of conductive materialfor receiving said hard leads and said soft leads, by forming solderedjunctions for connecting said first circuit elements and said secondcircuit elements to each other, comprising the followingsteps:assembling said first circuit elements on said metal board means,locating each of said eyelet terminals in a predetermined respectivehole formed on an unsolderable supporting mounting tool, mounting saidsecond circuit elements on said mounting tool by inserting each of saidsoft leads into a respective one of said eyelet terminals, insertingeach of said hard leads of said first circuit elements also into arespective one of said eyelet terminals, applying molten solder toportions of said hard leads and of said soft leads extending out of saideyelet terminals so as to connect electrically and mechanically saidfirst and second circuit elements at soldered junctions formed by saideyelet terminals; and removing said mounting tool from said solderedfirst and second circuit elements by passing said soldered junctionswith the eyelets through said holes.
 2. The method of claim 1, whereinthe step of assembling said first circuit elements on said metal boardmeans comprises mounting solder elements (54) of specified shape andsaid first circuit elements on said metal board means at predeterminedpositions, and soldering said first circuit elements to said metal boardmeans by passing said metal board means through conveyor furnace means.3. The method of claim 1, further comprising the steps of cuttingundesired portions (64) of said hard leads and of said soft leadsextending from said soldered junctions, and re-applying molten solder torepair cut portions of said soldered junctions.
 4. The method of claim1, wherein said applying of molten solder is done by using dip-solderingor wave-soldering techniques.
 5. The method of claim 3, wherein saidsteps of applying and reapplying molten solder involve introducingmolten solder into the inside portion of said eyelet terminals bycapillary action.